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Looking for a (good) Signetics 2504

Submitted by swapple on July 7, 2008 - 11:20pm. Apple I

Hello All.

My Obtronix Apple 1 reproduction has a bad Signetics 2504. I built the kit a while ago, but I think I would have noticed the problem then. So I guess it got tired!

The Signetics 2504 is a 1024-bit dynamic shift register, 8-pin dip. It's used here to as part of the display control. The problem I saw was odd numbers (1,3,5,7,9,A,C,E) in every other screen column were displayed as the preceding ASCII character (0,2,4,6,8,@,B,D). Data from the keyboard was stored correctly in main RAM. It was just the video memory was displayed incorrectly.

Anyway, does anyone have a source of a Signetics 2504?

logjam- a long time ago, you said you had a source for the 25xx chips. Are they still around?

Thanks!!
Scott Austin

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SchwindS's picture

Here you find the DataSheet of the Signetics 2504

Submitted by SchwindS on July 8, 2008 - 7:30pm.

Here is a link to one of my favorite Apple I Website's

There you find a Datasheet of the Signetics 2504
I hope it made it easyer to find a spare part for your Apple I

&gt
http://www.cpmuseum.com/Library.aspx?Section=Apple/Apple-1/IC%20Reference%20Guides

SchwindS

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May be very hard to find just

Submitted by Mike WIllegal on July 10, 2008 - 11:32am.

May be very hard to find just one of these parts. Looks like you need a Signetics 2504v, which some of the larger obsolete part vendors list as in stock. However they usually have high prices and require a minimum purchase of something like $300.00. It may be worthwhile entering a RFQ to a few of them to see what their actual price and minimum purchase requirements are. Another approach may be to find out if some other period device of lessor value used the same part and scavenging one of those. I have found a few vendors that stock some old and obsolete parts and sell small quantities, but none of these list 2504 as in stock. Just the same, I'll list them here for future reference for the group.

advanced components electronics (ACE) http://www.acecomponents.com/
unicorn electronics http://www.unicornelectronics.com/
anchor electronics http://www.demoboard.com/anchor.htm

Regards,
Mike Willegal

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Thanks for the good links. I

Submitted by swapple on July 11, 2008 - 5:32am.

Thanks for the good links. I'll keep looking!

BTW, I just completed my Obtronix Apple 1 reproduction. I'll be starting a new thread in a minute.

Scott

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